The wind sector is increasingly becoming a fundamental sector for sourcing power and in particular, since it is part of the renewable energies, it also constitutes a strategic source for the development and the progress of a country. This is where the present innovation comes in, attempting to substantially enhance the electric power acquired from a certain airflow for the same other conditions, with respect to wind generators known at the state of art.
A typical wind generator consists of a wind turbine adapted to rotate around a rotational axis and an electric power generator, for example an alternator, coupled with the wind turbine so as to convert the rotation energy of the wind turbine into electric power. In particular, the wind turbine has a rotation shaft that is coupled with the rotor of the alternator so as to transfer to the rotor rotational kinetic energy generated by the wind incident on the blades by interposing a step-up gear.
In general, wind turbines can be split between those having a vertical axis and those having a horizontal axis.
Horizontal axis wind turbines generally have a higher efficiency than vertical axis ones, even if they have two basic limitations, which are the limit introduced by the Betz theory and the need of a step-up gear located on the shaft of the turbine, respectively.
Concerning the first limitation, it derives from the axial impulse theory which, based upon the energy balance and upon the amount of motion, it leads to a maximum power coefficient Cp equal to 0.593; by adopting other more complex theories, like for example the vortex impulse theory, the coefficient can reach maximum values up to Cp=0.69.
Concerning the second limit, it derives from the need of having a step-up gear in order to be able to introduce the power acquired in the network of the National supplier (Mains frequency 50/60 Hz). Typically, the shaft of the turbine rotates at an angular velocity of between 10 and 30 revs/min whereas the electric power generator requires a higher rotation speed, depending upon the configuration of the generator and particularly upon the number of poles. The transmission ratios vary on average between 50 and 100 with variable efficiency between 0.6 and 0.65.